Circuit arrangements with a programmable memory element are used in various fields of circuit and electronics technology, for carrying out particular functions in different applications. The particular functions in this context are determined by the data or programming codes stored in the respective programmable memory element or elements. Such programmable memory elements can be reprogrammed simply by storing different data or programming codes therein. Thereby, it is possible to alter or entirely replace the original data or programming codes, which have been stored in the programmable memory element by the manufacturer, for example. However, such a reprogramming of the memory element by changing the stored data or programming codes, especially by unauthorized persons, is often not desired.
One field of application in which such circuit arrangements with at least one programmable memory element are typically used is in the engine controller of a motor vehicle. The data and programming codes stored in the memory element are the basis of the control functions carried out by the engine controller. It has become known that the engine performance characteristics of a motor vehicle can be altered or specially “tuned” by reprogramming the memory element of the engine controller circuit, and a special automobile tuning after-market has developed in this regard. It is also possible to change the engine performance characteristics by so-called “chipping”, i.e. by removing the original equipment memory element and replacing it with a differently programmed memory element. In any event, such specialty tuning of the engine controller circuit arrangement aims to enhance the engine performance with respect to the maximum torque or maximum horsepower or the power curve, for example, but often while detracting from or totally removing various safety related functions such as the maximum engine speed (r.p.m.) limiting, or fuel economy, or exhaust gas emissions, for example. Generally, these electronic tuning efforts require ready access to the programmable memory element or at least the conductor paths connected to the contacts of the memory element, for carrying out the reprogramming.